Global navigation satellite systems (GNSS) are already widely known in the prior art. GPS (Global Positioning System) is an example thereof. Here, on the basis of the signals received from several satellites, a current position is determined, for example, by means of a mobile telephone or a motor vehicle.
Especially in motor vehicles there are more and more vehicle systems that require the most exact possible determination of the current position of the motor vehicle. This relates particularly to vehicle systems in the field of motor-vehicle-to-motor-vehicle communication (c2c communication) and in the field of motor-vehicle-to-infrastructure communication (c2x communication). For this use, the precision of the GNSS position provided by conventional GNSS receivers is not sufficient, since the uncertainty is too high. Therefore, in the prior art, methods have already been proposed for improving the positional precision based on the use of a GNSS.
DE 10 2008 020 446 A1 relates to the correction of a vehicle position using distinctive points. Therein, it is proposed to detect distinctive points, that is to say landmarks, wherein the distinctive points are stored in a database in the vehicle together with associated exact GPS positions. Therefore, a correction of the position finding is possible on the basis of the data in the database.
However, this approach has the disadvantage that exact surveying of landmarks is exceedingly difficult and expensive. A comprehensive use of surveyed landmarks for improving the determination of the position via a GNSS is therefore currently not feasible. In addition, the precision of the GNSS receivers and thus of the GNSS positions determined by them is highly dependent on the environment, so that, for example, the precision on the highways where there is a free line-of-sight connection with the satellites is considerably higher than in the skyscraper canyons where the line of sight to the satellites is greatly limited or not at all directly possible. In the example of the skyscraper canyons, the GNSS signal, if it reaches the receiver at all, reaches it only by way of the so-called multipath propagation, which in turn enormously worsens the precision that can be achieved. Therefore, in such areas landmarks would be much more appropriate than in other areas.